1. Field of the Invention
The present invention relates to a disk apparatus for reproducing information data recorded in an optical disk such as a DVD (Digital Versatile Disk) and, more specifically, the invention relates to a disk apparatus capable of distinguishing the kinds of optical disks easily and accurately.
2. Description of the Related Art
In recent years, as a recoding medium for recording and reproducing information data, there has been used an optical disk having a large recording capacity. A rewritable optical disk includes not only a CD-RW (Compact Disk-ReWritable), a DVD-RW (ReWritable) and the like but also a DVD-RAM (Random Access Memory). However, the DVD-RAM is different in format from other optical disks: that is, a CAPA (Complimentary Allocated Pit Address) area and a data recording area are provided in each sector; in the data recording area, there are formed wobble-shaped grooves and lands; and, in the CAPA area, there are previously recorded address pits alternately at positions shifted by ½ track from each other with respect to the grooves or lands (see FIG. 2). Therefore, when reproducing information data recorded in the DVD-RAM, the signal processing of the disk apparatus must be adapted to the format of the DVD-RAM. Thus, it is necessary to distinguish whether an optical disk loaded into the disk apparatus is a DVD-RAM or other optical disks than the DVD-RAM, which makes it impossible to shorten the time for starting the reproduction of information data recorded in the optical disks.
As the background art, there is known a disk apparatus in which an optical pickup is swept in the focus direction to detect the peak and bottom values of the total internal reflection add signal of a reflected light received by the optical pickup, and the presence or absence of an address pit is checked to thereby distinguish the kinds of the optical disks (for example, see JP-A-2005-38514).
Also, conventionally, there is also known a disk apparatus in which the total internal reflection add signal of a reflected light received by an optical pickup is binarized, the presence or absence of an address pit is detected from the number of times of outputs of the binarized signals or from intervals between the outputs thereof, and the kinds of optical disks are distinguished according to the presence or absence of the address pit (for example, see JP-A-2004-46977).
Further, conventionally, there is known a disk apparatus in which an envelope signal is detected from an RF signal read out from an optical disk, the amplitude of the envelope signal is detected in an off tracking state, and, using the thus detected amplitude, the kind of the optical disk is distinguished (for example, see JP-A-2000-285582).
Moreover, conventionally, there is also known a disk apparatus in which whether an optical disk is an optical disk belonging to a specific kind or not is determined from a focus search level and, further, the kind of the optical disk is distinguished from the level of a focus error signal (for example, see JP-A-2000-315355).